Apple posted a Leopard guided tour video, in the same format as the earlier iPhone and iPod Touch guided tours. It mentions the new Finder, stacks, Time Machine, Quick Look, Spaces, and so on. In Quicktime, of course.

I'm getting tired of hearing this. What exactly amazing features do people want other than a more polished and well functioning OS?

What I imagine the GP is missing (and me too, to be honest) are the "top secret features" that Steve couldn't tell us about when he first demoed Leopard because they were just too cool and Redmond was going to copy them. And what did they turn out to be? I honestly don't even remember, though I was expecting something like "Time Machine brought to you by ZFS." During WWDC I was mostly busy being embarrassed for Apple by the transparent menu bar and 3D Dock. Two big steps back in usability, all to bring teh prettiez.

Anyway, there's tons of new stuff in Leopard to recommend an upgrade. I pre-ordered my copy the day Apple announced the ship date, mostly on the anticipation of the new Xcode tools and the better multithreading OS-wide. And contrary to what seems to have been the experience of many here who watched the video guide and didn't see anything new, I saw lots of "hey, that's really nice" features that I hadn't heard about before. Not top secret, and not, by themselves, $129, but a solid step forward when taken together.